"The Reactivity of Carboxylic Acid and Ester Groups in the Functionalized Interfacial Region of 'Polyethylene Carboxylic Acid' (PE-CO2H) and Derivatives: Differentiation of the Functional Groups into Shallow and Deep Subsets Based on a Comparison of Contact Angle and ATR-IR Measurements", Holmes-Farley, S.R., and Whitesides, G.M., Langmuir, 1986, 3, 62-76. PDF